Syftet med detta projektarbete var att minska energiförlusterna i Getrag All Wheel Drives hypoidväxlar (se kapitel 7.2.3). Uppdraget bestod främst av att minska förlusterna när systemet endast driver på två hjul och de övriga hjulparen endast överför låga kraftmoment, detta förhållande benämns draggmoment. För att kunna utvärdera och peka på förbättringsområden var första steget i arbetet att lokalisera och värdera enskilda komponenter som tillförde förluster. De ingående komponenter som studerades grundligt var lager, Kuggkontakt, olja och tätningar. Värderingen av komponenternas respektive förlustbidrag erhölls genom provning och beräkningar. Provningen bestod dels av tidigare utförd provning och dels av provning utförd under arbetets gång. För beräkning av lager och tätningar användes beräkningen från lagertillverkaren SKFs egna beräkningsmodeller. Beräkning av hypoidväxelns smörjningsförluster skedde enligt ISO/TR 14179-2. Övriga beräkningar härleddes genom tribologiska formler med givna friktionskoefficienter. När ingående komponenter var värderade genom beräkningar och provning valdes de komponenter som tillförde de största förlusterna att utvecklas vidare. Vald komponent att förbättra blev lager, där förspänningen av lageranordningen mellan kronhjulsaxeln och aluminiumhus studerades. Utöver lagerförspänningen undersöktes även inverkan av oljans viskositet på lager och växel som helhet. Resultatet från konceptgenereringen resulterade i en lösning där en aluminiumring ska monteras mellan två koniska rullager på röraxeln för att bibehålla den initiala förspänningen mellan dessa lager under förhöjda temperaturer. Detta bidrar till att kunna sänka den initiala förspänningen. Genom användning av en förspänningsring av aluminium kan initial förspänning enligt analys och beräkningar sänkas från 13 kN till cirka 6 kN. Enligt beräkningar minskar momentförlusterna i lager på röraxeln då med 0,36 Nm. Det Andra konceptet var att välja en olja med lägre viskositet än dagens produktionsolja och på så vis erhålla en minskning av momentförluster. Från en kinematisk viskositet på cirka 45 mm2/s till en kinematisk viskositet på 33 mm2/s vid 80 °C minskades RDU-växelns(bakre hypoidväxel) totala förluster i lager med 0,53 Nm. Rekommendationen för fortsatt arbete blev att börja utföra grundliga tester för en olja med lägre viskositet och sedan om godkända resultat erhålls byta ut dagens växelolja. Samt att i ett senare skede genomföra provning med en förspänningsring om ytterligare förbättrad verkningsgrad önskas.

Lubrication is critical in order to achieve high efficiency and reliability of machine elements such as gears, bearings, and other moving mechanical assemblies (MMA). In space applications, tribological properties of lubricants are quickly growing more important. Traditional space systems such as satellites imply MMA such as gyroscopes, antenna pointing mechanisms, and solar array drives. These MMA operate in high vacuum (<10-5 Pa) under lightly loaded conditions. Modern space missions on the other hand, such as remotely operated vehicles used for in-situ Mars exploration relies on different types of MMA. In these robotic systems, electromechanical actuators are being used extensively to provide controlled motion. Gears and bearings in these actuators operate in an atmosphere mainly consisting of CO2 at ~10+3 Pa under heavily loaded contact conditions. In these conditions, the tribosystem is likely to operate in the boundary lubricated regime, with consequent risk of high friction and wear. High molecular weight fluids have significant heritage in space because of their low vapor pressure. They are currently employed as lubricants in a wide range of space applications, as they meet high demands on resistance to vacuum outgassing. Unfortunately, the large molecules are susceptible to degradation under heavy load. Ionic liquids (ILs) on the other hand, are synthetic fluids that consist entirely of ion pairs with opposing charge. The resulting ion bonds enable inherently low vapor pressure of the fluid without the need for a high molecular weight. For this reason ILs have been advocated as potential lubricants for space applications, but so far compatibility issues have hampered their use as lubricants. Countless IL variations are possible, and solutions are thus likely to exist. Constituent ions can be designed individually and combined in various configurations. However, the fundamental understanding of the lubricating mechanism of ionic liquids is still incomplete, and consequently the optimum molecular structure for IL lubricants remain unknown. In this thesis, a stepwise approach to molecular design of IL lubricants is described, and the resulting hydrocarbon-mimicking ionic liquids are evaluated in tribological experiments. In this thesis, the experiments focus on tribological performance, using steel-steel tribopairs in air environment under boundary lubrication (Paper I). Boundary film formation under a range of contact pressures and temperatures, is analyzed after tribotesting by optical profilometry, scanning electron microscopy (SEM), and energy dispersive X- iii ray spectroscopy (EDS) in Paper II. The analysis reveal formation of a highly effective boundary film based on silicate, that can be further enhanced by amine additives. This thesis demonstrates the feasibility of improving tribological performance of ionic liquids by molecular design. / Projekt: Rymdforskarskolan 2015

The constant pursuit in the automotive industry to increase the engines performance, new solutions are always developed and tested to reduce the friction and increase the efficiency in the engine. One component that contributes to friction losses is the piston ring pack where the top compression stands for up to 40 %. This master thesis collaborated with Scania’s material science department Basic engine and covers the friction and wear of four different materials on the cylinder liner surface against the top compression ring.The four tested materials were grey cast iron with different honing quality and three atmospheric plasma sprayed coatings with titanium oxide, chromium oxide and Metco’s mixture F2071 which is a stainless steel mixed with a ceramic. A martensitic steel piston ring with a chromium coated sliding surface was used for all the testing in the Cameron-Plint TE77 test-rig. This is a pin-on-disc test method and the parameters used for testing is set to replicate the environment the ring is exposed to at the top dead centre.The test-rig has been in Scania’s possession for a long time and has not always given a satisfying result. An uneven contact between the ring and liner has been a problem resulting in only worn edges of the liner specimen. The piston ring holder was therefore redesigned to be able to adjust the radius of the ring. This allowed a good conformability between the ring and liner to be obtained.The tested materials were evaluated according to friction and wear. Friction was measured with the test-rig and the wear was calculated with surface profiles that were measured before and after testing. Worn surfaces were studied in a SEM to verify which wear mechanism that was active. The changes of the surfaces was studied with the use of following surface parameters Ra, Rk, Rpk, Rvk and if there was a connection between these parameters and friction and wear coefficient.Independent of honing quality showed the grey cast iron lowest friction coefficient just under 0.13, the F2071 liner showed a friction coefficient just above 0.13. Both oxide layers showed similar friction where the chromium oxide had a friction just below 0.15 and the titanium oxide lay just above 0.15. Lowest wear coefficient had the chromium oxide followed by F2071, titanium oxide and the bad honed grey cast iron. These three liners showed almost the exact same wear coefficient. Worst wear coefficient had the grey cast iron with a good honing quality. A mild abrasive wear mechanism was active during the wear test and vague wear marks was found on the surface. There is no connection between wear coefficient and friction and the change in surface roughness during the test does not affect the friction.

The present work deals with developing a tribological test machine that had been built earlier but did not function properly. It was giving out abnormal noises and vibrations and was not corresponding to its desired functions. In this study, the root of these problems is analyzed and some solutions are suggested by developing a new construction concept for the machine.

Working at elevated temperature has its challenges due to the high level of complexity whenthe tribosystems operate under harsh conditions, commonly resulting in an increase on thefriction and thermal softening that goes into severe adhesion, severe abrasion and materialtransfer. Despite considerable research, there is a lack of research on tribology applied to hightemperature processes.  The aim of this project is to understand the tribological behavior of tool steel sliding againstaluminum under lubrication conditions working at high temperature. Salt-based, graphite-based, and polymer-based lubricants were evaluated as they are commonly used for aluminum forming. The cleanability of the lubricants after being subjected to elevated temperatures is also studied. High temperature tribological tests were carried out in a reciprocating sliding flat-on-flat configuration for 15 seconds. Optical microscope, SEM and EDS were performed to analyze the specimens after the tribological tests. Then a cleanability study was done to evaluate the cleanability of the lubricants and the effect of temperature on the cleanability of the lubricant. The concentration of the lubricants played an important role in the lubricant’s friction stability and dispersion, particularly for the polymer-based and graphite-based lubricants. Under the tested conditions the salt-based lubricant was ineffective as it showed high and unstable friction. The 10 wt.% polymer-based lubricant concentration presented severe adhesion and material transfer from the aluminum onto the tool steel.  The effect of temperature on the cleanability of the lubricants was correlated to the temperature in which the lubricants start to degrade. Nevertheless, the best cleanability was achieved when using ethanol as a cleaning agent in combination with high pressure spraying, and wirebrush techniques. Mild and high alkaline agents had poor cleanability abilities resulting insurface damage and corrosion on the tool steel.

The purpose of the project work was to build knowledge of the tribological behaviour of self-lubricating laser cladding, with and without external solid lubricant during conditions relevant for hot metal forming of aluminium. The materials used during the project were plates coated with a Ni-based self-lubricating clad and a reference sample of work tool steel. The self-lubricating laser clad was applied using a high power direct diode laser. The external solid lubricant used was a graphite dispersion. The external solid lubricant was applied on the samples using a spraying technique, leaving a dry layer of solid graphite on the plates. To test the tribological behaviour of the plates, linear reciprocating friction and wear tests were performed both under lubricated and dry conditions. During the dry tests, different surface roughness of the plates where investigated. The pins for the tribological test were made of AA7075. Parameters chosen for the tribological tests were based on conditions during hot forming of aluminium. After having taken images of the plates using scanning electron microscopy, and using a 3D optical profiler, the wear volume and material transfer was evaluated, and wear mechanism analysis was performed.   The tribological behaviour of polished Ni-based laser clad under dry conditions is comparable to that of the reference sample at its best performance. Using a mirror polished Ni-based laser clad under dry condition can be an option to not using external solid lubricant during hot forming of aluminium. Also, the surface roughness of the self-lubricating clad under dry conditions does not affect the coefficient of friction.

Wear is a commonly occurring degradation mechanism for materials and components in the rock drilling industry. The wear can occur by either abrasion or adhesive wear. Further corrosion and presence of water or other lubricating fluids with or without particles may influence the behavior. Which mechanism, or mechanisms, and under which conditions it occurs, as well as the relative wear rate is dependent on the actual operating conditions for the component. In the present study, commonly available and general test methods for wear on high-alloy carbon steel has been analyzed. The project has been carried out through literature reviews and study visits at the tribology laboratory at KTH and at the Angstroms laboratory at Uppsala University. The present study indicates that it is difficult to suggest a feasible test method that is possible to use for all different situations of the wear that may occur. A test adapted to the actual situation is required to achieve a proper wear rate comparable to the wear rate in a real application.  According to the requirements from Ovako AB, a test that is general, cost effective and can be used when developing steel with higher wear-resistance, following wear testing methods has been compared: a pin-on-disk apparatus, a dry/wet sand/rubber wheel, a dry/wet sand/steel wheel, a tumbling mill, a particle erosion rig, a solid particle impingement using gas jets and a grinding machine. The tumbling mill, the grinder and the “Standard Test Method for Wear Testing with a Pin-On- Disk Apparatus” correspond to the requirements best. Ovako AB is recommended to continue the work with these testing methods. / Nötning är en vanlig mekanism som orsakar nedbrytning på material i gruvindustrin. Nötningen kan förekomma som abrasiv eller adhesiv nötning. Korrosion och närvaro av vatten eller andra smörjande vätskor med eller utan lösa partiklar kan påverka beteendet. Den eller de mekanismer som styr nötningen såväl som nötningstalet beror på de aktuella förhållanden vilka materialet eller materialen verkar i. I denna studie har en generell testmetod för att utvärdera nötning på höglegerat kolstål har undersökts. Arbetet har genomförts genom litteratursökning samt studiebesök vid tribologiska laboratoriet på KTH samt på Ångströmska i Uppsala. Utifrån arbetet har det visat sig att det inte förekommer några generella nötningstest för alla applikationer, då det krävs ett test som är anpassat efter verkligheten för att få ut korrekt nötningstal. Utifrån Ovako ABs önskemål om ett generellt test som är ekonomiskt hållbart samt kan användas för att utveckla nötningsbeständigheten i de stål där nötning förekommer har följande testmetoder jämförts: pinne/skiva-maskin, blött/torrt sand/gummihjul, blött/torrt sand/stålhjul, roterande trumma, ”Erofugen”, partikelsprutare och en slipmaskin. De test som motsvarar kravprofilen bäst är den roterande trumman, slipmaskinen samt den standardiserade pinne/skiva-maskinen. Utifrån dessa testmetoder rekommenderas Ovako AB att fortsätta arbetet.

Efficient transmissions systems are key to producing competitive motor vehicles that have a smaller environmental impact. Gears are the main components in vehicle transmissions and although they are already highly efficient, there is still room for improvement. In this study, the focus falls on the lubricant used to create separating films between gears and todissipate heat. When driving, the gears churn this lubricant, giving rise to power losses that are related to the amount and properties of the lubricant. However, any attempt to reduce these losses must not compromise the required lubrication and heat dissipation. Paper A reports on the use of an FZG gear test rig to investigate power losses and heat generation for different gear immersion depths, surface roughness and coatings. The results show that lower gear roughness reduces gear mesh losses and heat generation. A polishing affect was obtained when a non-coated gear ran against a coated gear.The aim of the research reported in paper B was to increase the accuracy of efficiency testing. It investigated how and whether repeated disassembly and re-assembly of the same test equipment, as well as test performance and rig conditions, affect the measured torque loss in an FZG gear test rig. It was shown that the measured torque loss changes between one assembly and another. Repeatability between tests is crucial for accurate conclusions.The aim of the research reported in paper C was to study whether gear efficiency could be increased by a running-in procedure, which would reduce the need for a coolant. A back-to-back gear test rig was used to test two running-in loads. Higher gear mesh efficiency was seen when a higher running-in load was used. / <p>QC 20141006</p>

Requirements today for machines have moved beyond functionality intoefficiency and reliability, gears are no exception. The presented work focuseson the analysis of the measurement, evolution and effect of running-in on geardrives from a surface roughness and efficiency point of view. With no consen-sus on a definition or observation of running-in of gear drives, measurementsof both efficiency and surface transformation during the predefined running-inis explored. A verified methodology on how to separate form, waviness androughness is presented. Two finishing methods, namely generation groundand superfinished, are analyzed in terms of efficiency and surface characteris-tics as manufactured, after running-in and after efficiency testing in order todetermine the effects of load level during running-in.Results show that separation of form can be achieved with a carefullychosen polynomial, while waviness is more subject to how the user definesa cut-off wavelength for the surface roughness. Ground gears show distinctsmoothening in terms of surface roughness at high running-in load, and nogeneral trend for low load. This behavior is also reflected in the efficiencysince higher loads gave overall lower efficiency after running-in when com-pared to lower loads. Superfinished gears in contrast show no running-in ef-fects in terms of efficiency. Additionally, ground gears exhibit general changein friction and surface roughness during the first cycles of running-in whenanalyzing high load. Overall gains in efficiency can be obtained from running-in; however, at most speeds improvements from polishing a surface, in thiscase superfinishing, proved to lead to higher efficiency. / <p>QC 20150922</p>

A common choice of bearing for industrial applications such as turbomachinery and rotating compressors is the Tilting-Pad Journal Bearing (TPJB) due to its excellent stability properties. TPJB's are however limited by the reduction of damping in the fluid film at high velocities. In order to overcome this, the Active Tilting-Pad Journal Bearing (ATPJB) has been developed. By adding the possibility of high-pressure radial oil injection through servo-valves which can be controlled via a feedback-loop control system, the classically purely mechanical TPJB becomes a mechatronic device called ATPJB.  The objective of this project is to conduct an experimental evaluation of the dynamical behavior of the ATPJB test rig located at the Technical University of Denmark, use the experimental results to modify the previously developed dynamical model which is used for the calculation of a model-based control system. The control system is to be implemented and experimentally validated at high velocities. Improvements made to the test rig in order to achieve high velocities have been documented and described in this work. The mathematical modeling of the individual components, reduction methods, and the global system assembly is covered with an extensive overview. Parameters of the model have been made frequency dependant in order to have an accurate model, resulting in good agreement with experimental data over a wider operational range. With the implemented Linear Quadratic Gaussian controller it is shown that ATPJB has extended operational range compared to TPJB and shows reduction of vibrations over rotational speeds spanning from 1000 RPM to 10,000 RPM. The ATPJB-technology, as it is implemented in this project, does not improve frictional losses in the system. It is argued that the added sensing and actuating systems inherited in the ATPJB technology make the technology highly suitable for the ideas of Industry 4.0 and also allows for the implementation of Early Fault Diagnosis which gives an economical incitement to invest in ATPJB-technology.